Battery and Motor Vehicle

ABSTRACT

A battery includes at least two battery cells and a first electrical connection between a first battery pole of one of the at least two battery cells and a second battery pole of one other battery cell of the at least two battery cells. A second electrical connection branches off from the first electrical connection for the purpose of measuring a battery cell voltage of at least one battery cell of the at least two battery cells.

This application claims priority under 35 U.S.C. §119 to patentapplication no. DE 10 2012 214 896.5, filed on Aug. 22, 2012 in Germany,the disclosure of which is incorporated herein by reference in itsentirety.

BACKGROUND

The present disclosure relates to a battery module having at least onebattery having battery cells, for example lithium ion battery cells,such as are used in traction batteries in electric or hybrid motorvehicles, thus in motor vehicles that are at least in part orintermittently driven in an electric manner. The disclosure thereforealso relates to a motor vehicle.

Batteries are being used in an increasingly wide range of applicationsdue to improved storage capacity, the ability to recharge morefrequently, increased energy densities and a reduced level ofself-discharge. Batteries that have a lower energy storage capacity areused for example for small portable electronic devices such as mobiletelephones, laptops, camcorders, power tools, mp3 players and similardevices, while batteries that have a higher capacity are used as anenergy source for driving motors in hybrid or electric vehicles etc. oras batteries in stationary applications.

Batteries can be embodied for example by way of the series connection ofbattery modules, wherein to some extent parallel connections of thebattery modules can also be provided and the battery modules can fortheir part comprise series connected and/or parallel connected batterycells.

Lithium ion technology can be used for a wide range of applications.Lithium ion cells comprise at least one positive and negative electrode(cathode and/or anode) that are capable of reversible intercalation orthen de-intercalation of lithium ions (Li+).

The intercalation of lithium ions and/or the de-intercalation of lithiumions require the presence of a so-called lithium ion conducting salt.Lithium hexafluorophosphate (LiPF6) is used as the lithium conductingsalt in most lithium ion cell-based batteries that are currently on themarket.

This applies both in the field of small portable electronic devices andalso in the motor vehicle industry.

Other known battery chemical systems are batteries that are based onnickel metal hydride cells, lithium metal polymer cells and lithiumpolymer cells.

In order to control the individual voltage and temperature of the cells,sensor lines are routed from the cell connections to a voltagemonitoring device, possibly to a cell monitoring circuit board.

In accordance with the prior art, the sensor lines are generallyembodied as cables or lead frames, wherein the lines have a smallcross-section. In the event of a short circuit, the complete line meltsas a result of the small cross-section.

SUMMARY

In accordance with the disclosure, a battery is provided having at leasttwo battery cells and having an electrical connection between a batterypole of one of the at least two battery cells and a battery pole of oneother of the at least two battery cells. A further electrical connectionbranches off from the electrical connection for the purpose of measuringa battery cell voltage at least of one of the battery cells.

The battery is characterized by virtue of the fact that the furtherelectrical connection comprises at least two sections, wherein thesections are embodied for different maximum current magnitudes.

This renders it possible to embody one of the sections as a fusible linkthat melts in the presence of a melting current magnitude that liesbetween the different maximum current magnitudes. Thus, in comparison tousing individual fuses, a safety fuse is provided in the cell monitoringsystem in a cost-effective and simple manner, which safety fuseseparates the connection in the event of a short circuit.

In one embodiment, the different maximum current magnitudes include atleast a lower maximum current magnitude that is less than a meltingcurrent magnitude and a higher maximum current magnitude that is greaterthan the melting current magnitude, wherein at least one of the sectionsis embodied as a fusible section for the lower maximum current magnitudeand melts in the presence of the melting current magnitude and at leastone other of the sections is embodied for the higher maximum currentmagnitude and does not melt in the presence of the melting currentmagnitude.

In an advantageous manner, it is possible to access the fusible sectionin order to perform a visual inspection.

Thus, the at least one other of the sections can be encased in asynthetic material casing and the fusible section can remain uncovered.

This improves the separating effect.

In one embodiment or in one other embodiment, the fusible sectionadjoins two of the other of the sections that have the higher maximumcurrent magnitude.

The main directions of expansion of two of the other of the sections canbe mutually parallel and two of the other of the sections can be spacedapart from one another at a distance that is greater than zero in adirection that is perpendicular to the parallel main directions ofexpansion.

It can be particularly advantageous for the separating effect if two ofthe other of the sections are spaced apart from one another at adistance that is at least three millimetres in the direction of theparallel main directions of expansion.

If a further fusible section adjoins one of the two of the other of thesections, then one of the two of the other of the sections can expand upto at least two millimetres in the direction of the parallel maindirections of expansion. Even if the separating effect is interrupted asa result of a voltage flashover after a first fusible section hasmelted, the melting of the first fusible section causes the otherfusible section to melt. Any further voltage flashover is then reliablyprevented as a result of the length of the section that lies between thefusible sections.

It is particularly advantageous for the separating effect if theexpansion amounts to up to five millimetres.

A vehicle having a battery in accordance with the disclosure is alsoproposed in accordance with the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the disclosure are further explained withreference to the drawings and the following description. In thedrawings:

FIG. 1 illustrates an exemplary embodiment of a battery in accordancewith the disclosure,

FIG. 2 illustrates a first exemplary embodiment of an electricalconnection for the purpose of measuring a battery cell voltage in abattery in accordance with the disclosure, and

FIG. 3 illustrates a second exemplary embodiment of an electricalconnection for the purpose of measuring a battery cell voltage in abattery in accordance with the disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates a battery 10 having two battery cells 20, 21 that areseries connected in an electrical manner by means of an electricalconnection 30. It is possible to provide a greater number of batterycells, wherein the battery cells can be mutually connected in seriesand/or in parallel. A further electrical connection 40 branches off fromthe electrical connection 30 to a voltage measuring means, notillustrated.

The voltage measuring means can be embodied for example as part of acell monitoring electronics system, part of a battery control device,part of a battery management system or part of the battery and issuitable for ascertaining a voltage between the branch and one of thebattery poles 11, 12 and thus for ascertaining a battery cell voltage atleast of one of the two battery cells 20, 21.

The electrical connection 40 comprises sections 41, 42 that differ withrespect to the maximum current magnitudes for which they are embodied ineach case. At least one of the sections 41 is embodied as a fusiblesection and melts in the presence of a melting current magnitude that isgreater than or equal to the maximum current magnitude of the fusiblesection but less than the maximum current magnitude of one or of severalother sections 42.

A current having current magnitudes between the melting currentmagnitude and the higher maximum current magnitude then causes a meltingreaction in the region of the fusible section 41 without causing anycorresponding changes in the region of the other section 42.

One option for achieving different maximum current magnitudes fordifferent sections of the connection 40 is to use differentcross-sections perpendicular with respect to the main direction ofexpansion of the respective section. It has proven to be successful inpractice to provide the fusible section with a cross-section that is 10%less than the other sections 42. A fusible section 41 that is one to tenmillimetres in length in its main direction of expansion demonstratedgood separating characteristics during tests.

Another option that can also be used together with a reducedcross-section is to use different materials. In particular, aluminiumhas proven to be a suitable material for the fusible section(s), sinceit is cost-effective and melts quickly in the event of an overload.

All the sections or only the fusible sections can be embodied as a leadframe.

In an exemplary embodiment, not illustrated in the figures, the branchof the connection 40 from the connection 30 is produced from aluminiumand embodied as a fusible section. The fusible section can be embodiedfor example at the transition from the connection 40 to a cable lug orto a terminal that is arranged on the connection 30. When using a foilcircuit board that is provided with conductor tracks that are embodiedfrom aluminium for the cell monitoring system, the fusible section canbe embodied as one of these conductor tracks.

FIG. 2 illustrates an exemplary electrical connection 40 forascertaining battery cell voltage together with sections 41, 42.

The connection 40 comprises two sections 42 that are encased by means ofa synthetic material casing 50 and are mutually connected by means of asection 41 that remains uncovered. The encased sections 42 adjoin onboth ends of the section 41 that remains uncovered. In one embodiment,the section 41 that remains uncovered has a smaller cross-section thatthe encased sections 42, wherein each of the cross-sections isperpendicular to a main direction of expansion of the respective section41, 42.

The fact that the fusible section 41 is not encased renders it possiblefor the fusible section 41 to be visually inspected in a simple mannerand to improve the separating effect after said fusible section hasmelted. On the other hand, the fact that the fusible section 41 isencased provides improved protection against the separating effect beinginterrupted as a result of electrically conductive objects or liquidsshould accidents occur.

In the exemplary embodiment illustrated in FIG. 2, the main directionsof expansion of the encased sections 42 are mutually parallel but offsetwith respect to one another in a direction perpendicular to the parallelmain directions of expansion. The encased sections 42 are spaced apartfrom one another at a distance 60 that is greater than zero in thedirection that is perpendicular to the parallel main directions ofexpansion. A main direction of expansion of the fusible section istherefore not parallel to the parallel main directions of expansion. Theexpansion of the fusible section in the main direction of expansion ofthe fusible section is thus greater than a further distance 70 that isgreater than zero between the encased sections 42 in the direction ofthe parallel main directions of expansion. A distance 70 of at leastthree millimetres represents a considerable reduction of voltageflashovers between the sections 42 after the fusible section has melted.

FIG. 3 illustrates a further exemplary embodiment of an electricconnection 40 for the purpose of measuring a battery cell voltage in abattery 10 in accordance with the disclosure. The connection 40 in FIG.3 comprises by way of example two fusible sections 41, a greater numberof fusible sections 41 is also possible. Both ends of each of thefusible sections 41 are adjoined by sections 42 that are connected in anelectric manner by means of the respective fusible section 41. The twofusible sections 41 shown in FIG. 3 are consequently adjoined on bothends by a middle section 42 and are connected in an electrical manner bymeans of the middle section 42. The fusible sections 41 are spaced apartfrom one another at a distance 80 that is greater than zero in a mainexpansion direction of the middle section 42. In practice, a fusiblesection spacing 80 of two to five millimetres has proven to besuccessful.

When a single fusible section 41 is used, an increase in expansion ofthe fusible section in the main direction of expansion reduces thenumber of voltage flashovers between the sections 42 after the fusiblesection has melted. When a plurality of fusible sections 41 is used, theamount of expansion of the fusible section can be small in the maindirection of expansion, in other words it can be selected in the rangefrom one or a few millimetres. When a plurality of fusible sections 41is used, the voltage flashover protection is provided by virtue of thefact after a plurality of sections 41 have melted the sections 42,between which the voltage flashover can occur, are additionally spacedapart from one another by the fusible section spacing 80.

In one embodiment, not illustrated, some or all sections 42 also remainuncovered. In a further embodiment, not illustrated, some or all thefusible sections 41 are also encased. Other exemplary embodiments do nothave a spacing 70 that is greater than zero between the sections 42.

What is claimed is:
 1. A battery comprising: at least two battery cells;a first electrical connection between (i) a first battery pole of one ofthe at least two battery cells, and (ii) a second battery pole of oneother battery cell of the at least two battery cells; and a secondelectrical connection configured to branch off from the first electricalconnection for the purpose of measuring a battery cell voltage of atleast one battery cell of the at least two battery cells, the secondelectrical connection including at least two sections, the at least twosections being configured for different maximum current magnitudes. 2.The battery according to claim 1, wherein: the different maximum currentmagnitudes include at least (i) a lower maximum current magnitude thatis less than a melting current magnitude, and (ii) a higher maximumcurrent magnitude that is greater than the melting current magnitude, atleast one section of the at least two sections is configured as afusible section for the lower maximum current magnitude, and is furtherconfigured to melt in the presence of the melting current magnitude, andat least one other section of the at least two sections is configuredfor the higher maximum current magnitude and is further configured tonot melt in the presence of the melting current magnitude.
 3. Thebattery according to claim 2, wherein it is possible to access thefusible section in order to perform a visual inspection.
 4. The batteryaccording to claim 3, wherein: the at least one other section is encasedby a synthetic material casing, and the fusible section is uncovered. 5.The battery according to claim 2, wherein the fusible section adjoinstwo sections of the at least one other section of the at least twosections that have the higher maximum current magnitude.
 6. The batteryaccording to claim 5, wherein main directions of expansion of the twosections of the at least one other section of the at least two sectionsare mutually parallel and are spaced apart from one another at adistance that is greater than zero in a direction that is perpendicularto the parallel main directions of expansion.
 7. The battery accordingto claim 6, wherein the two sections of the at least one other sectionof the at least two sections are spaced apart from one another at adistance that is at least three millimetres in the direction of theparallel main directions of expansion.
 8. The battery according to claim5, wherein: a further fusible section adjoins one of the two sections ofthe at least one other section of the at least two sections that havethe higher maximum current rating, and the one of the two sections ofthe at least one other section of the at least two sections has anexpansion factor of at least two millimetres in the direction of theparallel main directions of expansion.
 9. The battery according to claim8, wherein the expansion factor is up to five millimetres.
 10. A motorvehicle comprising: a battery including at least two battery cells, afirst electrical connection between (i) a first battery pole of one ofthe at least two battery cells, and (ii) a second battery pole of oneother battery cell of the at least two battery cells, and a secondelectrical connection configured to branch off from the first electricalconnection for the purpose of measuring a battery cell voltage of atleast one battery cell of the at least two battery cells, the secondelectrical connection including at least two sections, the at least twosections being configured for different maximum current magnitudes.